Really Bad Constant Vibration Problem New Install HELP!

[Lennyd123]

Short Version: The boat has become the worlds largest foot massager from 1000-3000 rpm either under way, or in not.

Long version: 7.4 454 B1 drive. After the third attempt to get a rebuilt engine purchased in 05 re rebuilt and finally done right, and finalize the perpetual re-powering of this boat, and countless thousands of dollars and hours later the engine is finally installed and the boat vibrates like nobodies business.

It does it in neutral, drive, reverse, turning left or right, going straight, and now I learned today after removing the outdrive it does it with no load as well.

It is really bad, and not that one would see from a bad gimbal bearing or u-joints while turning (still doing it with the drive removed eliminated them anyway) and it is literally driving me nuts.

Please offer your thoughts on this as everything I have come up with (as well as the mechanic involved) has not helped, and the changes proposed do not make any sense (eg. motor mounts etc) as they have little to do with being out of balance which is what causes vibes.

Except for the engine rebuilder missing something I am at a total loss here, and since it took a few months for the mechanic to actually swing this thing in I am really not looking forward to having to remove the engine again as it could cost the season.

I have been directed to the coupler, mounts, alignment, and others, but I cant see it being the mounts making it vibe, and the alignment should not come into play with the drive removed. I guess the coupler could be out of balance and be the cause, but it was fine previously, and even during initial break in before install there was not any obvious vibes.

Oddly after reaching planning speed the vibes reduced until barely noticeable, but upon throttling back the vibes increased violently to the worst levels.

I am running out of ideas, and cash as well so I wanted to reach out to you guys for help (ideas not cash lol) as I do not want to follow the path of changing out parts until we trip over the one causing the problem. Plus all of the proposed fixes not only include some pricey items, but also removing the engine once again, and I do not want to go through that just on a whim or guess.

So can a previously good coupler throw an engine out of balance? Would the builder be a good or better place to start just to be sure he did not leave anything out that could cause it? Is there anything I can check that I have missed?

Any help is welcome, and most appreciated!!

 

[Eric 3.7LX Alpha 1]

Re: Really Bad Constant Vibration Problem New Install HELP!

You also experience the vib. with the drive off, just running the engine?

 

[rodbolt]

Re: Really Bad Constant Vibration Problem New Install HELP!

sounds like someone used an incorrect match on the crank and flywheel.
at the rebuild were the original crank,flywheel and harmonic balancer reused?

 

[Lennyd123]

Re: Really Bad Constant Vibration Problem New Install HELP!

Yes vibe is there w drive on, drive off, and when running. It does reduce greatly once on plane and above 3K rpm.

I was leaning towards the crank being an issue as the shop that did the rebuild had commented on the fact that my 454 did not have the pin or dowel in the crank like it should have, and that it was the 427 that did not use it.

Going to have an good talk with that shop on monday to see what he can offer as suggestions, but much as it is looking that he may have missed needing to balance the crank with the pin etc I am really not looking forward to having to pull the whole thing again, and also having to start pushing them to get it done so I do not lose any more time.

My mechanic that did the install seems to be pushing for changing out all the little stuff still, but I can not see how front motor mounts could cause the vibe, and even though the next part he wants me to buy is could cause vibes because it is part of the rotating mass etc the coupler should not have gone bad when the boat was not being used, and it was spending most of its time in storage waiting on either the rebuilder or the installer etc.

Since this is the third time in 5 years I am trying to get this damn thing right (have to admit I am almost to the point of being able to prep it to be removed and also hook everything up with my eyes shut lol) and have more into the repower than the damn boat is worth and am also starting to get low of $$$ I am not wanting to use the shade tree mechanic approach to correcting this (buying new parts till the problem goes away etc).

Any thoughts on the coupler, mounts, and also what should I be looking for with the crank and flywheel??

Thanks!!

 

[Lennyd123]

Re: Really Bad Constant Vibration Problem New Install HELP!

"were the original crank,flywheel and harmonic balancer reused"

The flywheel and balancer were from the original 1990 MCM 7,4. and the crank is what was supplied from the original rebuilder when I purchased the rebuilt engine.

I had explained this to the new shop doing the recent rebuild as I was feeling like it could be a clusterfux" of bastard parts, and wanted them to confirm everything mated up correctly, but am starting to think they got busy and just slapped it all back together.

On the positive side the original rebuild would not rev, sounded like a diesel from a valvetrain problem, and ultimately the exh valves and pistons were making contact in all cylinders, but now at least the thing runs, and will rev up enough to get on plane, but you have to be strong willed to get past the vibes.

To add insult to injury another boating friend stopped by and reminded me that prior to all of this insanity I was complaining about a small vibe during sharp turns, and now look at what I am stuck dealing with.

This is getting crazy

 

[rodbolt]

Re: Really Bad Constant Vibration Problem New Install HELP!

over the years GM used both internally balanced cranks and externally balanced.
the cranks took different balancers and flywheels.
cant remember all the details but the crank forging numbers will tell you.
if it vibrates,not an engine miss, with the drive off I would not suspect a coupler but something on the reciprocating/rotating parts.

 

[300sflyer]

Re: Really Bad Constant Vibration Problem New Install HELP!

Sounds to me that the original rebuild shop used the wrong crank and/or flywheel... I see no other solution other than to pull the engine again, and start checking it over. Not what you wanted to hear I know...

 

[jtmarten]

Re: Really Bad Constant Vibration Problem New Install HELP!

If its not a situation where a plug or two aren't firing, incorrect firing order, etc., I'd say it sounds like a mismatch of internal/external balanced crank, flywheel, and balancer.

 

[300sflyer]

Re: Really Bad Constant Vibration Problem New Install HELP!

Yes indeed... Do check the firing order before you pull it!

 

[HVAC Cruiser]

Re: Really Bad Constant Vibration Problem New Install HELP!

If you have a 427 crank in the block with 454 pistons you have other problems. The 396/427 has a 3.76 stroke internal balance & the 454 has a 4.0 stroke external balance, same rods, different pistons ( wrist pin distance). Your deck height would be off for start. The 427 and 454 are the same block though. As others stated check your firing order, after that start looking at the harmonic balancer and flywheel. The balancer is the quickest to tell, you don't have to pull the engine. The 454 balancer right off the bat is 8" and the 396/427 is 7". If you look at it a 454 balancer also has a hollow on one side on the circumference whereas the 396/427 dont . I can take a pic of one if you want if that would help. I have a few laying around.

Edit- this is what a 454 balancer looks like notice the step in it

- the rust hopefully LOL

Hope it helps, thats where I would start

 

[rodbolt]

Re: Really Bad Constant Vibration Problem New Install HELP!

and the pic of that balancer is different than both the 2000 7.4MPI volvos I have on the shop floor.
there was also a 366 or 377 truck engine that shared some components with the 454.
they look alike and some parts physically interchange but wont work.
big difference in deck height.
bout all I can remember from years ago.

 

[HVAC Cruiser]

Re: Really Bad Constant Vibration Problem New Install HELP!

and the pic of that balancer is different than both the 2000 7.4MPI volvos I have on the shop floor.
there was also a 366 or 377 truck engine that shared some components with the 454.
they look alike and some parts physically interchange but wont work.
big difference in deck height.
bout all I can remember from years ago.

The ones I posted were from Chevy 454's. Do the marine ones still have that recess to balance the engine? Maybe snap a pic for him to get him started figuring out his mess

 

[Lennyd123]

Re: Really Bad Constant Vibration Problem New Install HELP!

over the years GM used both internally balanced cranks and externally balanced.
the cranks took different balancers and flywheels.
cant remember all the details but the crank forging numbers will tell you.
if it vibrates,not an engine miss, with the drive off I would not suspect a coupler but something on the reciprocating/rotating parts.

I was aware of the different set ups GM used though not an expert by any means on what they all were and what could be used together etc , and I explained the suspect parts to the rebuild shop before the engine was even disassembled.

Since after speaking with the rebuilder and learning he was not 100% on what was balanced, if it was balanced to the dowel pin, and am waiting for monday morning to get into it again I am suspect of them using the correct combination.

I have checked the firing etc, and nothing I could do seemed to make any changes in the vibes, but sort of wish it did cause that would be an easier fix.

Going to change out plug wires and most likely the coil as well very soon, and needed or not as it can not hurt and there aging some anyhow, but doubt it is going to have an effect on the vibes. Even though most parts were new somewhere between 05-07 and have less than an hour or so on them etc I ended up using the original coil which was my spare as there was a problem with the newer one from over tightening one of the lead screws. So more for peace of mind than anything else.

I hope this guy can determine what the correct combination should be for this crank/engine (it is a two piece rear seal like the original set up) as this place was excellent in the past with working on many jobs I had while rebuilding small engines (bikes, atv's etc) and never had a single problem or complaint.

Now what is interesting is that I have allowed my mechanic to nearly convince me to buy new front mounts as he believes that my old rusted together, non movable, non adjustable, and perfectly aligned ones may not be absorbing enough of the vibes, but in my mind from years of working with industrial equipment and various balancing issues it is not as much about absorbing the vibes or shock etc, but eliminating it so that there is no additional wear on other mating parts.

Not sure if I should even bother, but the mounts are cheap enough and easy enough I guess?? What you all think on this???

Also I was told by the mechanic that there are only two different marine flywheels for the BBC application, and that they have different bolt patterns and really can not be mixed up. Does this sound accurate, and should we concentrate on the balancer, and dowel pin???

Thanks some more

 

[Lennyd123]

Re: Really Bad Constant Vibration Problem New Install HELP!

Sounds to me that the original rebuild shop used the wrong crank and/or flywheel... I see no other solution other than to pull the engine again, and start checking it over. Not what you wanted to hear I know...

Your not kidding that is not what I wanted to hear, but to make matters worse none of these guys move to fast either, and getting the two coordinated so that there is still a 2010 season is going to be a trick

I hope that after my talk with the rebuilder on Monday that we can find a way to make it a priority, and be ready so that it may be as easy as changing the balancer, or adding the pin to the crank, but it just never seems to work that way for me.

On the positive side were getting this down to a science, and are running about 30-45 minutes to get it pulled or installed once this guys fork truck fires up

 

[Lennyd123]

Re: Really Bad Constant Vibration Problem New Install HELP!

Yes indeed... Do check the firing order before you pull it!

Checked and re-checked.

Believe me I was praying someone messed up the firing order.

 

[Lennyd123]

Re: Really Bad Constant Vibration Problem New Install HELP!

If you have a 427 crank in the block with 454 pistons you have other problems. The 396/427 has a 3.76 stroke internal balance & the 454 has a 4.0 stroke external balance, same rods, different pistons ( wrist pin distance). Your deck height would be off for start. The 427 and 454 are the same block though. As others stated check your firing order, after that start looking at the harmonic balancer and flywheel. The balancer is the quickest to tell, you don't have to pull the engine. The 454 balancer right off the bat is 8" and the 396/427 is 7". If you look at it a 454 balancer also has a hollow on one side on the circumference whereas the 396/427 dont . I can take a pic of one if you want if that would help. I have a few laying around.

Edit- this is what a 454 balancer looks like notice the step in it

- the rust hopefully LOL

Hope it helps, thats where I would start

Wow great info THANKS! THANKS! THANKS!

First off both of those balancers look brand new compared to this one, and I am going to have to look seriously closely to see if there is any resemblance of the cut out on the OD.

Another issue is that since I relied on the shop to get it right, and explained it all to them etc, I did not get into the internals at all, and though deck heights, stroke, bore and even the combined affects they have on compression, squish, combustion and the like are familiar topics from setting up the small engines (long story but not all bike and ATV engines are nearly perfect and miss a lot of potential power etc, but again long story lol) so I have no idea on this engine, but it is looking like I had better start getting involved more if this is going to work out.

A couple related questions.

If the balancer was corroded to the point that the hollow is not noticeable would it still be able to do its job??

If it really was the correct 8" and has been reduced to 7" (or close to it etc) would it still be able to do its job?

Now I know these are a biotch to pull from previous experience, so could it be done with the engine still in place (there is a good amount of side room, but not so much forward room in this bilge) without one losing what little patience and mind he has remaining??

Also can any of you guys confirm that there are only two marine flywheels (I believe this one is the original) and that only one actually fits the 454 crank? I hope that is the case as it would help to prove (with out internal parts removal) which crank it is, and where the attention needs to be for correcting the problem (balancer, or weight/dowel pin in rear of crank), and is this thinking even close to being correct???

Thanks again for all your help, and I am going to see what pics I may have to help you all help me, and I really mean THANKS!



Here are two of the best pics I have showing the balancer. Sorry for the really sad looking engine, but this was what I received back from the marina who did the original install of the Hesco rebuild back in 2005 (thanks whities landing you guys are real pro's). Hope it can help etc.

 

[Lennyd123]

Re: Really Bad Constant Vibration Problem New Install HELP!

I looked at those pics I posted, and realized there is not much in the way help since they just show a bunch of rusted up steel.

Will take a look at the balancer tomorrow when I am going over some other stuff, and will also post a better pic if I can get one.

Also can someone confirm my memory on the crank PN being on the rear outside flange?

I am starting to be concerned with the potential for miss matched parts due to the original rebuild/assembly causing the exhaust vales to be hitting the pistons. But I think from what HVAC posted it should actually be the opposite of this since the piston would not be coming up far enough in the cylinder.

Will see what I can find from the rebuild shop tomorrow as I expect they have some part numbers etc.

Thanks again guys!!

 

[Lennyd123]

Re: Really Bad Constant Vibration Problem New Install HELP!

Was able to get a measurement on the balancer today, and it is looking like approx 7-3/4 to 7-7/8. It was tough to get an accurate measurement with the pulley attached, and I confirmed the approx size by adding the pulley OD to the amount remaining on each side etc.

I guess the difference from the anticipated 8" is from corrosion and removing the worst of it etc.

No luck with questioning the rebuilder today. Not sure if it was bad timing or ????.

Could the seriously corroded, and now lighter balancer be unable to do its job, and part of the problem, if not the problem? OK maybe just hopeful thinking, but hey you never know lol.

 

[bruceb58]

Re: Really Bad Constant Vibration Problem New Install HELP!

I sure thought that all 454s were balanced externally. You should check the flywheel to make sure there are weights on it. A flywheel from a 400 will bolt right on but the 400 is internally balanced. How do I know this? My parents had a flyweel replaced on a suburban and the mechanic put a 400 flywheel on it. It eventually broke the crank.

 

[Lennyd123]

Re: Really Bad Constant Vibration Problem New Install HELP!

I sure thought that all 454s were balanced externally. You should check the flywheel to make sure there are weights on it. A flywheel from a 400 will bolt right on but the 400 is internally balanced. How do I know this? My parents had a flyweel replaced on a suburban and the mechanic put a 400 flywheel on it. It eventually broke the crank.

That is the end result I am really trying to avoid

Far as I know the flywheel, and balancer are from the original MCM 7.4, but then I would have no way to know if any of the people who worked on these rebuilds swapped them out either.